14. The mutation causing the recessive disease allele for sickle-cell anemia rem

Question

14. The mutation causing the recessive disease allele for sickle-cell anemia removes one MstII restriction site from the globin gene so that a probe, instead of hybridizing to two fragments of 1.1 kb and 0.2 kb, hybridizes to one 1.3-kb fragment. For two parents to have a 25 percent chance of a child with sickle-cell anemia

A) they must both show only fragments of 1.1 and 0.2 kb.

B) they must both show fragments of 1.3 and 0.2 kb.

C) one must show only a 1.1- and the other only a 0.2-kb fragment.

D) one must show a 1.3- and the other a 1.1- and a 0.2-kb fragment.

E) they must both show all three types of fragments.

Explanation / Answer

Given that, the parents have a 25 percent chance of a child with sickle-cell anemia, means both are carriers. Observe the below cross between two carrier parents.

Ss* Ss = SS, Ss, Ss, ss (25% affected children).

B) they must both show fragments of 1.3 and 0.2 kb. (Since both carry the mutation).

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